Biomedical subjects

R G Chadwick

Publications and source records attributed to R G Chadwick.

At least 19 recordsLinked to original sources

PubMed2005

Maxillary incisor palatal erosion: no correlation with dietary variables?

The objectives of the study were to examine a relationship between tooth erosion affecting the palatal aspects of permanent maxillary central incisors with dietary, behavioral and medical variables. The methods included, 251 schoolchildren aged 11 to 13 years were recruited to participate. Each subject had dental impressions of the palatal aspects of both upper central incisors recorded at baseline, 9 and 18 months intervals. From these, electroconductive replicas were fabricated, mapped and compared using a surface matching technique. At the end of the study all participants underwent a structured interview that sought to assay the level of potential erosive dietary, behavioral and medical risk factors. Correlation analyses of the responses given in the final structured interview with the degrees of palatal tooth substance loss (both previous and measured) were under taken. The results showed: (1) The degree of previous erosion did not predict the level of measured ongoing erosion. (2) Brushing the teeth more frequently with fluoridated toothpaste correlated significantly with lower levels of ongoing erosion (P = 0 011). It was concluded that: (1) Evidence of previous palatal erosion did not predict future erosion. (2) The application of topical fluoride as a by-product of tooth brushing may provide an element of protection against palatal erosion. (3) In view of the lack of correlation between exposure to potential risk factors and the level of ongoing palatal tooth surface loss in this study, other factors (such as an individual's susceptibility and salivary buffering power) may well be more important predictors. The clinical relevance included: Preventive advice to patients with dental erosion should not only include the use of topical fluoride, in the form of toothpaste, but recognize individual susceptibility to this condition.

Adolescent↗

PubMed2004

Linear interpolation error in measured surfaces in a dental erosion study.

An extensive palatal erosion study, which is currently being undertaken at the University of Dundee, aims to detect erosion through the precise mapping of replicas of children's incisors. All perceived sources of error are being scrutinised closely. The error due to the interpolation of surface positions from discrete point measurements has been investigated so that its contribution to the erosion estimates can be gauged. The calculation of the error statistics made use of covariance functions to express the undulation of the tooth surfaces. It has been found that, for the measurement point spacing of 150 microm being used in the current project, the interpolation error for an incisor is typically about 25 microm, to be compared with the root-mean-square error due to tooth impression and replication procedures, assessed as being in the order of +/- 3 microm, and replica measurement, assessed as being in the order of +/- 5 microm. The interpolation error constitutes a surprisingly large proportion of the overall system error. The same error estimation technique can be applied usefully and without difficulty to other research studies concerning erosion or wear in natural or restorative dental surfaces.

Child↗

PubMed2004

Rationalization of quantitative tooth surface loss data for epidemiological research.

Recent UK National Surveys have revealed a high prevalence of tooth surface loss (TSL) because of erosion in Children and Adolescents. Although digital surface mapping and surface matching techniques may be used to quantify its progression with time, reporting TSL of individuals as a function of either mean depth loss or volume loss, this can be inadequate when transferred for epidemiological analysis. For example, a tooth displaying multiple regions of depth loss may deserve to be distinguished from a tooth with a single localised area of erosion, although the total volume change may be the same. A potential solution, explored here, is to use both the quantitative wear data and colour coded surface representation plots generated by such methods to arrive at a single categorical wear score [1 (< or = 5% of surface exhibits TSL) to 5 (> or = 51% of surface exhibits TSL)]. Two examiners independently categorized, on two separate occasions, the TSL of 53 maxillary incisors (26 subjects observed at baseline and 9 months). Their performance was assessed for intra- and inter-examiner agreement by; (i) calculating the percentage of agreement, (ii) a Wilcoxon matched-pairs signed rank test. Thereafter, in cases of disagreement a consensus score was allocated and a regression analysis of this versus the numerically derived percentage of the surface that had undergone change was carried out. Intra- and inter-examiner agreement was 100 and 88.7% respectively and for the inter-examiner comparison P = 0.0456. The categorical scores and the quantitative wear data correlated linearly (R = 0.82). It is concluded that the method used to rationalize the quantitative TSL data is both reproducible and reflects the quantitative data. Its use should be helpful in epidemiological TSL studies but continued vigilance is required in cases of examiner disagreement.

Adolescent↗

PubMed2004

A novel approach to evaluating the reproducibility of a replication technique for the manufacture of electroconductive replicas for use in quantitative clinical dental wear studies.

The assessment of the progression of tooth surface loss has until recently been limited to either the application of subjective ranking scales or visual comparison of sequential study casts. The development of quantitative measuring techniques offers the potential of greater accuracy and sensitivity. As direct intra-oral measurement is problematical such approaches often utilize impressions of the teeth, recorded at different epochs, to construct replicas for mapping and comparison. This in vitro investigation sought to determine the reproducibility of such an approach taking into account the total process chain. Two inlay cavities (one large, one small) were prepared in the palatal aspect of a plastic maxillary central incisor and restored with two flush fitting inlays. A series of impressions of this tooth were recorded, using a special tray and an addition cured light bodied silicone impression material (President, Coltene, Switzerland), with (a) both inlays in (b) both inlays out (c) large inlay out and small inlay in (d) large inlay in and small inlay out - a total of 16 impressions. Electroconductive replicas were fabricated from these and mapped using a computer controlled probe. Each series simulated wear of the tooth. A surface matching and difference detection algorithm was then used to compare each series of replicas and calculate the proportion of the surface undergoing simulated wear by a direct comparison of (a) matched to (b) or, indirectly as the summation of the results of matches of (a) with (c) and (a) with (d). The mean proportion of the surface with wear calculated directly was 26.6% (s.d.=0.6) and indirectly 26.1% (s.d. = 0.5). A one-way anova revealed no significant difference (P > 0.05). It is concluded that determining wear by this method is highly reproducible.

Algorithms↗

PubMed2003

Peer review amongst restorative specialists on the quality of their communication with referring dental practitioners.

OBJECTIVE: A peer review study was carried out to assess the written communication between consultants and specialist registrars in restorative dentistry with the referring general dental practitioners. METHODS: Seven people took part in the study and each presented referral and reply letters for five patients whom they had seen for consultation. The referral letters were used for information only and were not used in the peer review process. Each participant inspected the referral and reply letters from the other six participants. The reply letters were anonymously peer reviewed by using a proforma containing agreed criteria in relation to appropriate factors to include in the reply letter. The reviewer also ranked the letter in relation to overall quality on a 1-10 point scale. RESULTS: It was found that the participants' letters generally conformed positively with the agreed criteria although there were some differences between individuals. There were particular problems identified in relation to tooth notation. Reply letters commonly used different forms of tooth notation to the referring practitioners. CONCLUSIONS: The ranking of the letters generally indicated that the participants' replies were judged to be favourable by their peers. There may be scope for continuing this study in relation to peer review by other groups of professionals, in particular practitioners in primary dental care.

Attitude of Health Personnel↗

PubMed2003

Assessment of a procedure for detecting minute levels of tooth erosion.

Over a period of some years, the components of a system for discerning erosion on children's teeth have been progressively developed, for use in an extensive project seeking correlations between erosion and various perceived risk factors. The aim was the detection of minute levels of erosion, based on mappings of the palatal surfaces of the maxillary central incisors in children. Significant challenges were encountered, the primary problem being the impracticality of placing control marks that would aid the realignment of successive measurements. The paper describes the erosion detection system and initial experiences based on the results of the first 100 subjects measured after 9 months. The procedures detected the occurrence of erosion of 50 microm magnitude on about one-quarter of the teeth over the 9 month period, at a precision estimated to be +/- 15 microm. The occurrence of some anomalous incidents prevented the procedure from being fully automatic, and it necessitated human examination of a graphical diagram derived from the surface matching program, but it was nevertheless superior to current practices of examining impressions or replicas entirely by eye.

Child↗

PubMed2003

Selection for vocational/general professional training--the Dundee undergraduate experience.

Vocational training has been mandatory within the dental profession since 1993 but, despite this, there is continued disquiet surrounding the application process. This paper collates and summarizes the experiences of applicants from one dental school, to inform debate and assist in the continued evolution of the process of application for vocational training.

Education, Dental↗

PubMed2002

Quality assurance by service quality--an industrial approach to monitoring course delivery.

OBJECTIVE: To evaluate the use of an adapted customer service quality questionnaire as a management tool in the delivery of an undergraduate phantom head course. DESIGN: Two questionnaires, based upon an industrial definition of quality service, were devised and distributed for completion by second year dental students attending the management of dental caries course. These were applied to the academic years 1997/98 and 1999/2000. The first questionnaire was prospective, administered prior to course commencement, and sought to ascertain the level of importance attached to each dimension of course delivery. The second was retrospective and measured the level of satisfaction with course delivery. By comparing the 1997/98 responses for both questionnaire types, areas requiring improvement were identified. Where these areas were emphasised prospectively as important by the 1999/2000 students' improvement measures were introduced. Their effect was assessed by the subsequent retrospective satisfaction questionnaire. RESULTS: In all cases the questionnaire return rate was 100%. Although across the academic years overall student expectations did not differ significantly (P > 0.05) the emphasis of different components was found to vary according to academic year. CONCLUSION: The application of this technique assists the course organiser to make objective decisions on improving course delivery based upon the shortfalls of the previous year and the pre-course expectations of the following academic year. The industrial model thus translated well to an educational context and should prove useful in continually improving course delivery.

Consumer Behavior↗

PubMed2002

Evaluation of the accuracy and reproducibility of a replication technique for the manufacture of electroconductive replicas for use in quantitative clinical dental wear studies.

This work sought to evaluate the accuracy and reproducibility of a replication process that formed electroconductive replicas from addition cured silicone impressions for the purposes of monitoring tooth surface loss. Replicas were constructed by painting the surface of impressions with one of three high silver content electroconductive paints [Electrocure (EC), RS Silver Paint (SP) and Electrolube (EB)] and, once dry, backing this up with a cyanoacrylate based gel material (Zapit) and die stone. For each paint an impression was recorded of a gauge block of known step height (1270 microm) and five impressions of the palatal surface of a laboratory standard maxillary central incisor were also recorded. All impressions were taken using an addition cured silicone impression material (President). The resultant electroconductive replicas were mapped using a computer controlled probe. This data was analysed to determine both the replica's step height and, using surface matching techniques, the reproducibility of the replication process. The mean step heights recorded were; EC=1268.43 (s.d.=12.09), SP=1267.09 (s.d. 1.77) and EB 1299.58 (s.d. 14.47). Both EC and SP recorded the step height to within 3 microm. In the repeat replication of the palatal surface of an upper central incisor SP maintained a greater constancy of surface topography (99.6%) that was statistically superior to both EC (P < 0.05) and EB (P < 0.01). The SP was therefore the preferred paint for this technique. Bearing this in mind the replication technique was both accurate and reproducible but vigilance, as to the selection of paint for the process, should be exercised so as not to affect the good accuracy and reproducibility of the technique.

Algorithms↗

PubMed2001

An evaluation of the flammability of five dental gloves.

OBJECTIVE: To assess the flammability of five brands of dental procedure glove. DESIGN: A total of ten gloves of each brand (Biogel-D, Premier Protectors, Roeko-D, Safeskin Satin Plus and Schottlander Low Allergy) underwent flammability testing. Five of these were tested as supplied (unwashed) and five following the application of the hand disinfectant Hydrex (washed). Each glove was stretched over a metal frame and the time to ignition, when exposed to a standardised butane flame, recorded. In addition, the thickness of each glove was also assessed by micrometer measurement. RESULTS: All the gloves tested ignited in less than 2.5 seconds. Two way analysis of variance revealed significant effects of glove type (P< 0.001) and treatment (P< 0.05), together with a significant interaction of these factors (P < 0.05), upon the ignition time. Washing Roeko-D gloves with Hydrex significantly (P< 0.01) retarded the ignition time compared with those in the unwashed state. Both the glove thickness and material type appeared to be related to ignition time. CONCLUSION: The work presented here demonstrates the acute and varying flammability of a range of dental procedure gloves. It should serve as a reminder to those who routinely use open flames whilst gloved of the dangers of this practice.

Dental Equipment↗

PubMed2001

Conduct of an algorithm in quantifying simulated palatal surface tooth erosion.

In order to test the ability of an algorithm to quantify simulated palatal erosion, a total of 10 extracted permanent upper central incisors were mounted in brass blocks. Baseline impressions were recorded using an addition cured silicone impression material in a metal impression tray. Once set and removed from the teeth, the impressions were coated twice with a high silver content electroconductive paint, applied using a brush, before being backed up with die stone to form an electroconductive replica. Each tooth was then subject to three treatments: application of phosphoric acid etchant gel for 60 s, application of etchant gel for 120 s and immersion for 3 h in Diet Coca-Cola*. After each one the replication process was repeated. Thereafter all replicas were mapped using a computer controlled electrical probe and the resultant digital terrain models (DTMS) compared using a surface matching and difference detection algorithm (SMADDA). Surface matching was unsuccessful only in one instance. As the duration of the insult increased, so did the proportion of the surface that underwent change to a maximum of 33.3%. Anatomical site was significantly (P < 0.05) associated with the susceptibility to erosion. The cingulum periphery appeared most resistant to this. The algorithmic approach offers much scope for monitoring dental erosion as acid dissolution of the tooth's surface appears to occur gradually. The cingulum region appears relatively more resistant to this process than other tooth sites and thus facilitates the process of surface matching. Further testing is however, required to determine precisely the algorithm's upper tolerance level.

Algorithms↗

PubMed2000

The thermal insulating effects of five dental gloves.

On occasions within the case reports of the various medico-legal defence organizations mention is made of burns to the oral soft tissues arising from contact with a heated instrument. Good cross infection control dictates that the dentist should be gloved whilst treating patients. No study has to date examined the thermal insulating effect of wearing dental procedure gloves although double gloving is known to blunt temperature perception. It was the purpose of this work to compare the degree of thermal insulation afforded by five makes of gloves (Biogel-D, Featherlite, Healthline, Microtouch and Tru-Touch). Measurement of temperature rises at 15, 30 and 60 s were made when a copper cylinder, at ambient room temperature, containing an iron/constantan thermocouple was placed upon a 2.35 kg aluminium block maintained at 50 degrees C by a thermostatically controlled electrical heating element. This measurement was initially performed, on 10 separate occasions, with the aluminium block and copper cylinder in direct contact (Control). This arrangement was then modified to investigate the effects of the various gloves by placing a circular mat of each glove material, harvested from the palm of each glove, between the block and cylinder. For each glove, 10 sets of observations were made using a different circular mat of glove material whose thickness had been previously determined. An analysis of variance identified highly significant (P<0.001) differences between the temperature rise of the control and experimental groups. The degree of thermal insulation afforded by each glove type appeared related to the glove thickness. This was confirmed by regression analysis but, although correlation coefficients of at least 0.91 were recorded, no single relationship best related these two quantities. Glove thermal insulating properties should be considered when selecting gloves for use in the surgery.

Analysis of Variance↗

PubMed1999

Factors influencing dental students to attend for eye examination.

This investigation sought to determine those factors influencing dental students to attend for eye examination together with the frequency of such tests and level of eyesight correction. A questionnaire was constructed and circulated to all clinical dental students attending lectures and practical classes in Dundee over a 1-week period. This ascertained the age and sex of the respondents and gathered information on what had prompted each individual to attend for eye examination. The knowledge of any visual problems and their correction was also ascertained. All 114 questionnaires that were distributed were completed. The mean elapsed time interval since the last eye examinations was 1.81 (standard deviation = 1.19) years. The frequency of attendance was not affected by gender. Those who had had their eyesight corrected were significantly (P < 0.01) more likely to attend for examination every 2 years than those without correction. Good eyesight is important for the practice of dentistry and, although this is well recognized, it is apparent that the need for regular testing has not been understood by all. Strenuous efforts should be made to ensure that this message is impressed upon dental undergraduates from an early stage in their careers so that they may undergo screening every 2 years throughout their professional careers.

Adult↗

PubMed1999

Presentation of quantitative tooth wear data to clinicians.

OBJECTIVE: The purpose of this study was to ascertain the ease of interpretation and usefulness of different modes of presenting quantitative tooth wear data to clinicians. METHOD AND MATERIALS: A questionnaire that sought to ascertain both the ease of interpretation and usefulness of different modes of presentation for monitoring tooth wear was distributed to 67 clinicians. These modes (contour maps, surface topography and difference plots, and color-coded surface difference plots) were a product of ongoing development that used a mathematic algorithm to detect and quantify wear of teeth with time. A follow-up questionnaire, based on a fusion of the desirable features of surface topography and color-coded surface difference plots, was distributed to 40 of the original respondents to ascertain any improvement in clarity. RESULTS: In all respects, contour maps were rated significantly more difficult to interpret and less useful than the other techniques evaluated. No significant difference was detected between the other modalities. The follow-up questionnaire demonstrated a significantly enhanced utility of the revised plot in informing the clinician as to the worn sites and quantity of wear. CONCLUSION: The combined mode of presentation seems an excellent way of presenting wear results to clinicians for clinical application.

Computer Graphics↗

PubMed1998

Can chemical softening agents minimize cavity enlargement during removal of failed anterior resin composite restorations?

This in-vitro investigation sought to identify the most effective softening agents for three commercial anterior resin composites (Prisma APH, Brilliant and Blend-a-Lux) from four potential agents (75% ethanol, polyacrylic acid, acetone and acetic acid), selected as having close solubility parameter values to BIS-GMA. The Vickers microhardness test was applied to samples before and following a 180 s application of each agent. In addition, the degree of cavity enlargement following removal of resin composite restorations, aged by thermocycling, was assessed by image analysis. Using the same method the influence of both colour match and the 180 s application of softening agents, in the optimum chemical/material combinations, upon this was determined. Analyses of variance revealed that significant (P < 0-01) reductions in surface microhardness occurred when 75% ethanol was applied to Prisma-APH and acetic acid to Blend-a-Lux. Removal of restorations of all materials resulted in highly significant (P < 0.001) increases in cavity size. Application of either 75% ethanol to Prisma-APH restorations or acetic acid to Blend-a-Lux did not alter this result. Thermocycling only produced a significant (P < 0.01) (McNemar Test) deterioration in shade match of the Prisma APH restorations but analyses of variance, for all materials, revealed that the observed changes in colour match had no significant (P < 0.05) effect upon the degree of cavity size enlargement. It is concluded that the application of softening agents to reduce cavity enlargement is not a viable clinical option.

Acetic Acid↗

PubMed1998

Attempted evaluation of three porcelain repair systems--what are we really testing?

Porcelain restorations are widely used in restorative dentistry with general success. On occasion however, fracture of the porcelain occurs. Sometimes a repair may be attempted using resin composite and one of the many bonding systems available. This in vitro investigation sought to determine and compare the shear bond strengths between a visible light-cured resin composite (Prisma TPH) and dental porcelain (Matchmaker Porcelain) for three different bonding systems (Scotchbond Multipurpose Plus (SMP); One-Step (OS); DenTASTIC (D)) with a view to conducting a larger study to assist in material selection. All measurements were performed one week following the preparation and storage of specimens in distilled water, at 37 degrees C, using a Universal Testing Machine at a crosshead speed of 0.5 mm/min. Although the mean shear bond strengths differed significantly (P < 0.05) (OS > SMP) and the Weibull modulus value of SMP was significantly (P < 0.05) lower than both OS and D the almost exclusive cohesive mode of failure observed, within the porcelain itself, suggested that the test was more a reflection of the quality of the underlying porcelain than the union under investigation. It was thus concluded that the shear bond strength test employed here, and in other studies did not truly reflect the shear bond strength at the porcelain/composite interface and that a more meaningful test should be developed. The observed cohesive failure may account for repeated clinical failures of porcelain repairs where bonding to an inherently flawed porcelain structure inevitably results in further failure.

Acid Etching, Dental↗

PubMed1998

Mathematical shape matching as a tool in tooth wear assessment--development and conduct.

The quantitative assessment of restoration and tooth wear usually requires fixed reference points from which measurements are made. In longitudinal patient follow-up the loss or erosion of such points may preclude measurement and an alternative approach is to seek regions of coincidence and conflict in digital models of before and after wear surfaces, with a continuous refinement of the parameters of the coordinate transformations, until the closest correspondence between them is found. A computer program has been written to implement the algorithm and assess the technique's capacity to find the match between surfaces both artificially generated and from tooth replicas recorded from patients at different epochs. The program was able to achieve the desired ends, demonstrating the utility of the technique in tooth wear assessment but identifying the need to refine the program further to enhance both its difference detection capabilities and level of automation. Examination of the theory and practical experience highlighted certain situations when user understanding is invaluable to ensure a satisfactory solution. This strengthened the investigators' resolve against reliance upon commercially based surface fitting programs whose basis may not be fully understood. Notwithstanding this surface matching is a powerful tool in the investigation of dental wear.

Algorithms↗

PubMed1998

Dental injuries during general anaesthesia: can the dentist help the anaesthetist?

Endotracheal intubation is widely used in anaesthesia. Although it offers many advantages to the anaesthetic management of patients, this procedure carries the possibility that damage to the teeth may result. Dental damage in fact accounts for one-third of all medicolegal claims against anaesthetists and, although this problem has been widely discussed in anaesthetic circles, few dental articles have addressed the problem.

Anesthesia, General↗